1. Field of the Invention
The invention relates generally to systems and methods for selective control of fluid flow into a production string in a wellbore. In particular aspects, the invention relates to devices and methods for actuating flow control valves in response to increased water or gas content in the production fluids obtained from particular production zones within a wellbore. In other aspects, the invention relates to systems and methods for monitoring flow rate or flow density at completion points and adjusting the flow rate at individual production points in response thereto.
2. Description of the Related Art
During later stages of production of hydrocarbons from a subterranean production zone, water and/or gas often enters the production fluid, making production less profitable as the production fluid becomes increasingly diluted. For this reason, where there are several completion nipples along a wellbore, it is desired to close off or reduce inflow from those nipples that are located in production zones experiencing significant influx of water and/or gas. It is, therefore, desirable to have a means for controlling the inflow of fluid at a particular location along a production string.
A particular problem arises in horizontal wellbore sections that pass through a single layer containing production fluid. If fluid enters the production tubing unevenly, it may draw down the production layer non-uniformly, causing nearby gas to be drawn down, or water drawn up, into the production tubing at an accelerated rate. Inflow control devices are therefore used in association with sand screens to equalize the rate of fluid inflow into the production tubing across the productive interval. Typically a number of such inflow governing devices are placed sequentially along the horizontal portion of the production assembly.
The structure and function of inflow control devices is well known. Such devices are described, for example, in U.S. Pat. Nos. 6,112,817; 6,112,815; 5,803,179; and 5,435,393. Generally, the inflow control device features a dual-walled tubular housing with one or more inflow passages laterally disposed through the inner wall of the housing. A sand screen surrounds a portion of the tubular housing. Production fluid will enter the sand screen and then must negotiate a tortuous pathway (such as a spiral pathway) between the dual walls to reach the inflow passage(s). The tortuous pathway slows the rate of flow and maintains it in an even manner.
Another conventional device is shown in United States Patent Application 2004/0144544, which discloses an arrangement for restricting the inflow of formation water from an underground formation to a hydrocarbon producing well. Between the underground formation and a production tubing located in the well, there is disposed at least one flow chamber connected to the production tubing. The flow chamber is open to inflow of formation fluid and in communication with the production tubing via an opening. The flow chamber is provided with at least one free-floating body with approximately the same density as the formation water. The free-floating body closes the opening (choking or reducing inflow) when formation water enters the flow chamber. It is believed that orientation of the opening with regard to adjacent sand screen orientations could be problematic and that the openings could be susceptible to plugging. Further, the disclosed device is described as adapted for reducing only water flow and thus cannot reduce gas inflow.
Thus, conventional inflow control devices currently lack an acceptable means for selectively closing off flow into the production tubing in the event that water and/or gas invades the production layer. The present invention addresses these and other drawbacks of the prior art.